1. Field of the Invention
The invention relates to a light emitting device, and more particularly, to a light emitting device with a better light emitting uniformity and efficiency.
2. Description of Related Art
A light emitting diode (LED) is a light emitting element constituted by a semiconductor material having group III-V elements. The LED has advantages such as long service life, small volume, high shock resistance, low heat output, and low power consumption. Thus, it has been widely utilized in indicators or light sources for household appliances and various instruments. In recent years, the LED has been developed towards multicolor and high brightness; therefore, its application scope has been expanded to large outdoor display boards, traffic signal lights, and the like. In the future, the LED may even become the main illumination light source with both power-saving and environment-protecting functions.
In the designs of conventional LED illumination modules, the light beam emitted by the LED is projected directly. In other words, the light beam generated by the LED has high directivity, and thus may result in unfavorable light uniformity and glares that would cause discomfort of the user. Moreover, when the LEDs of multiple colors are combined, as the light from these LEDs is emitted forward directly, a large light mixing area is needed to harmonize the light. The size of the whole LED illumination device is increased as a consequence, which causes inconvenience.
To resolve the aforementioned problems, optical glass is usually cooperated in the current LED illumination modules, so that the light beam emitted by the LED can be utilized effectively. However, if the optical glass is covered on the LED, then an illumination angle generated by the entire LED illumination module may be too small or focused at a certain region, while even having problems such as non-uniform light or low color render index of the light source.